What is the bit rate in $bits/sec$ for a signal with $16$ quantization levels and a sampling rate of $8 \, kHz$?

Carrier waves are used for communicating signals over long distances because:

Which of the following is a man-made signal?

$A$ $TV$ tower has a height of $100 \ m$. The average population density around the tower is $1000 \ \text{per} \ km^2$. The radius of the earth is $6.4 \times 10^6 \ m$. The population covered by the tower is:

Match Column $A$ (layers in the ionosphere for skywave propagation) with Column $B$ (their height range).

Column $A$	Column $B$
$A$. $D$-layer	$I$. $250-400 \ km$
$B$. $E$-layer	$II$. $170-190 \ km$
$C$. $F_1$-layer	$III$. $95-120 \ km$
$D$. $F_2$-layer	$IV$. $65-75 \ km$

In amplitude modulation of waves,the maximum amplitude is $30 \text{ mV}$ and minimum amplitude is $5 \text{ mV}$,then the modulation index is